Ionic liquids are liquid organic salts or mixtures of salt consisting of organic cations and organic or inorganic anions and having a melting point of less than 100° C. Additionally inorganic salts and/or additives may be solved in these ionic liquids. These ionic liquids exhibit some very interesting characteristics, e.g. having a very low, virtually non measurable, vapor pressure, a high liquidus range, good electrical conductivity, and interesting solvation characteristics. These characteristics may predestine ionic liquids for several applications, e.g. as solvents (for example, in organic or inorganic synthesis, transition metal catalysis, biocatalysis, multiphase reactions, photochemistry, polymer synthesis, and nanotechnology), extracting agent (for example, liquid-liquid or liquid gaseous extraction, sulphur removal during crude oil processing, removal of heavy metals during water processing and liquid membrane extraction), electrolytes (for example, in batteries, fuel cells, capacitors, solar cells, sensors, in electrochemistry, electroplating, electrochemical metal processing, electrochemical synthesis, electroorganic synthesis, and nanotechnology), lubricants, thermofluids, gels, reagents for organic synthesis, in the so-called “green chemistry” (e.g. as replacement for volatile organic compounds), static inhibitors, specific applications in chemical analysis (e.g. gas chromatography, mass spectroscopy, capillary zone electrophoresis), and liquid crystals, etc. More details may be found in “Rogers, Robin D.; Seddon, Kenneth R. (Eds.); Ionic Liquids—Industrial Applications to Green Chemistry, ACS Symposium Series 818, 2002; ISBN 0841237891” and in “Wasserscheid, Peter; Welton, Tom (Eds.); Ionic Liquids in Synthesis, Verlag Wiley-VCH 2003; ISBN 3527305157”. The characteristics of ionic liquids may be adapted to any desired application by varying the respective anions and cations. Due to this wide variety of possible characteristics ionic liquids are often called “designer solvents”.
However, in many applications possible impurities, pollutions or contaminations of the ionic liquid may cause disadvantageous effects.